Project Summary/Abstract Concussion, a traumatically induced brain injury, is described by the Centers for Disease Control as a serious public health problem. Currently, management protocols are based on consensus and expert opinion, rather than high quality evidence, potentially resulting in difficulty in diagnosis and identification of physiologic recovery. The use of objective and quantitative measurements to better understand the etiology of concussion symptoms and the efficacy of intervention protocols may allow investigators to improve post-concussion care. Symptoms such as headache, dizziness, or cognitive difficulties commonly occur after concussion and likely relate to cerebrovascular dysfunction. Cerebral autoregulation, cerebral reactivity, and neurovascular coupling represent three areas of cerebrovascular function that are impaired after a concussion and relate to the presence of specific concussion symptoms. Cerebrovascular functioning may also relate to higher order cognitive functions, such as executive functioning. Combined gait and cognitive tests (dual-tasks) can probe executive function abilities, and can also objectively reveal post-concussion deficits. Thus, improved understanding of how concussion symptomology, cerebrovascular function, and gait function relate to one another will help in the objective monitoring of recovery. Additionally, rehabilitative strategies in concussion care have remained relatively ineffective, particularly when initiated soon after injury. Sub-maximal aerobic exercise is one potential rehabilitative strategy to improve cerebrovascular function, locomotor performance, and executive functioning, in addition to alleviating post-concussion symptoms. Therefore, we seek to examine 52 symptomatic adolescents within two weeks of a concussion on measures of symptom severity, cerebrovascular function, gait, and executive functioning. Participants will be pseudo-randomized into an 8- week sub-maximal aerobic exercise intervention or usual care, and physical activity intensity and duration will be objectively monitored with a heart rate monitor. Accordingly, we will 1) determine the relationship between symptoms, cerebrovascular function, gait, and executive function soon after a concussion, and 2) investigate the effect of an aerobic exercise intervention protocol on concussion recovery. We believe this represents an important line of research as few studies have used quantitative and objective measures to examine the efficacy of concussion treatments, and our study design will allow us to observe how post-concussion aerobic exercise initiated soon after injury affects recovery trajectories. Thus, improved understanding of the role of physical activity after concussion may eventually pave the way to develop better therapeutic interventions, and eliminate ?one therapy for all? treatments.